1. Field of the Invention
The invention relates generally to fiber-optic systems. More specifically, the invention relates to a method for aligning optical fibers to a lens array.
2. Background Art
Fiber-optic lightwave technology has found enormous application in long-distance communication. Copper wires and coaxial cables, and even microwave relays and satellites in some cases, are being replaced by fiber-optic systems. Fiber-optic links have several advantages over their metallic-based counterparts. These advantages include lower loss, higher information-carrying capacity, lower cost per channel, and a smaller physical mass. Currently, fiber-optic links carry hundreds of terabits per second over distances greater than 1,000 km. Even though this is orders of magnitude beyond the capacity of metallic links, the demands of global communication are driving the system capacity to double every year. To meet these demands, techniques such as wavelength division multiplexing (WDM) are being used to increase the transmission capacity of the fiber-optic link.
In WDM systems, many optical signals at different wavelengths are combined into a single beam for transmission in a single optical fiber. At the exit of the fiber, a demultiplexer is used to separate the beam by wavelength into independent signals. In communication networks employing transmission formats such as WDM, a cross-connect is needed to selectively route individual optical signals to different destinations. An Nxc3x97N cross-connect is a switch fabric that can switch a signal from any of N transmission lines to another of the N transmission lines. In optical networks, the majority of the signal routing is still performed electronically. This requires frequent optical-to-electrical and electrical-to-optical signal conversion, which slows down the network. To take full advantage of speed and bandwidth of optical signal transmission, an all optical network is required.
One approach to large-scale optical cross-connect, e.g., 1024xc3x971024 cross-connect, is based on free-space (three-dimensional) micro-optic switching. In micro-optic switching, the optical signal from a channel is re-routed by an array of micro-electronic (MEMS) actuated mirrors or prisms to any of the other output channels and then focused back into the output fiber by an array of collimating lenses. For free-space micro-optic switching, the optical fibers need to be arrayed and aligned with the array of collimating lenses. The challenge in making this type of cross-connect is aligning a large number of optical fibers to a large lens array and preserving that alignment. Prior art methods for aligning fibers to a lens array involve gluing or splicing an optical fiber to a substrate with an array of collimating lenses. FIG. 1 shows a prior art example wherein a fiber 2 is bonded to a substrate 4 by epoxy 6. The substrate 4 carries a collimating lens 8. For an Nxc3x97N cross-connect, Nxc3x97N such fiber-substrate connections would have to be made.
Connecting the fiber to the substrate by gluing or splicing requires serial alignment of each fiber in the array, which is a very time consuming process for a large-scale optical cross-connect. This has often hindered the development of large-scale optical cross-connects. Therefore, a more efficient method for aligning a large number of fibers to a large lens array is desired.
In one aspect, the invention relates to a method for aligning optical fibers with an optical component which comprises making a lens on an end of each optical fiber to form a microlensed fiber and arranging the microlensed fibers such that an optical axis of each of the optical fibers is oriented along a common direction. The method further includes positioning each lens a selected distance from the optical component so as to couple light into and out of the optical component.
In another aspect, the invention relates to an optical component which comprises a plurality of optical fibers arranged in an array and aligned along a common direction. Each of the optical fibers has a lens attached to an end thereof. The optical component further includes a body having an array of holes for receiving the array of optical fibers.
In another aspect, the invention relates to a multichannel component which comprises an optical component and a plurality of optical fibers arranged in an array and aligned along a common direction. Each optical fiber has a lens attached to an end thereof. The lens is positioned a selected distance from the optical component so as to couple light into and out of the optical component.
In another aspect, the invention relates to a device for an optical cross-connect which comprises a microlens array and an array of microlensed fibers positioned a selected distance from the microlens array to couple light into and out of the microlens array.
Other aspects and advantages of the invention will be apparent from the following description and the appended claims.